Flame cup



July 22, 1969 J. SPIERS ET AL FLAME CUP 4 Sheets-Sheet 1 Filed Aug. 8, 1967 lorneys July 22, 1969 J, SPIERS ET AL FLAME CUP 4 Sheets-Sheet 2 Filed Aug. 8, 1967 i T! I MJLMQQ A tl qm eys United States Patent 3,456,627 FLAME CUP John Spiers and Mathoor S. R. Panikkar, Peterborough, England, assignors to Perkins Engines Limited, London, England Filed Aug. 8, 1967, Ser. No. 659,083 Claims priority, application Great Britain, Aug. 11, 1966, 35,940/66 Int. Cl. F02b 19/08 US. Cl. 12330 3 Claims ABSTRACT OF THE DISCLOSURE An insertable flame cup in a pre-combustion chamber of a compression ignition internal combustion engine. The flame cup which has a floor and an upstanding wall, an inlet aperture in the floor and an adjoining outlet aperture in the wall influences combustion, power and torque output, and smoke level by creating a desirable turbulence in the compressed gaseous charge.

Background of the invention It has been proposed to initiate ignition of combustible charge in compression ignition internal combustion engines in a pre-combustion chamber which is connected to the associated cylinder by a restricted passage or throat. The completeness of combustion and in turn the power and torque outputs and smoke level in such engines is de pendent, among other things, on the nature of the turbulence of the compressed gaseous charge immediately before and after injection of fuel into the pre-combustion chamber.

To simplify formation of such pre-combustion chambers in engine cylinder heads it has been proposed to form the chambers from a bore closed at one end by the metal of the cylinder head and at the other by an insertable flame cup which forms the bottom wall or floor of the pro-combustion chamber.

Summary of the invention As the construction of the flame cup has a considerable effect on the turbulence of the charge, it is an object of the present invention to provide a flame cup for use in forming a pre-combustion chamber in a compression ignition internal combustion engine which chamber possesses desirable inflow and outflow characteristics resulting in improved engine performance and/ or reduced smoke level.

According to the invention there is provided a flame cup for use in forming a pre-combustion chamber in a compression ignition internal combustion engine, the cup having a floor and a continuous upstanding wall, an inlet aperture in the floor and an adjoining outlet aperture in the wall, the floor having a channel portion which is inclined downwards towards the outlet aperture from a region remote ttherefrom and which terminates in a vertical face defining the inlet aperture.

Preferably, said inlet aperture is wider than said channel and the flank portions which define aid channel terminate at the inlet aperture in vertical faces flush with and one on either side of the vertical face which terminates the channel itself.

The invention also embraces a compression ignition internal combustion engine incorporating a flame cup according to either of the two immediately preceding paragraphs. In this case the cylinder head of the engine is preferably formed with a groove which forms an extension of and is generally parallel to the floor of said channel portion and provides a connecting passage 3,456,627 Patented July 22, 1969 hoe Brief description of the drawings FIG. 1 is a vertical sectional view of part of the cylinder head of a compression ignition internal combustion engine showing a precombustion chamber closed by an insertable flame cup;

FIG. 2 is a top view of the flame cup;

FIG. 3 is a view on the arrow -III in FIG. 2;

FIG. 4 is a view on the arrow 1V in FIG. 2;

FIG. 5 is a perspective view of the flame cup from above and in the direction of arrow V in FIG. 2;

FIG. 6 is a perspective view of the flame cup from above and in the direction of the arrow VI in FIG. 2;

BIG. 7 is a view similar to FIG. 2 of a modified flame cup; and

FIG. 8 is a graph of engine characteristics.

Detailed description of the preferred embodiments Referring .to the drawings, there is shown in FIG. 1 part of an engine cylinder head 10 in which a combustion chamber 11 is formed by a bore 12 extending into the head from beneath and fitted with a flame cup 13 of heat resisting alloy. The bore of the combustion chamber is dome shaped at its upper end and is recessed at 14 to receive the walls of the flame cup. One such pre-combustion chamber is provided for each cylinder of the engine.

Each chamber 11 is connected to its associated cylinder by a vertical throat 15 formed by an elongated aperture in the base of the flame cup. The area and exact shape of the aperture when viewed in plan (FIG. 2) may be varied in accordance with required engine performance.

A horizontal secondary or outlet aperture 16 is formed in the lower part of the wall of the flame cup 13 at the throat 15 and adjacent to this outlet aperture 16 the head 10 is recessed or grooved at 17 as seen in FIG. 1 to direct the hot or burning charge in the desired direction.

The interior wall of the flame cup 13 forms a smooth extension of the combustion chamber wall, and the floor of the flame cup is provided with a channel 20, the floor of which slopes downwards between flank portions 21 towards the main throat 15 to form a ramp which is substantially parallel to the grooved portion 17 of the head 10. The ramp terminates abruptly in a vertical edge 19 which forms a wall of the throat 15. I

In operation, during the compression stroke of the piston, air is directed upwardly through the throat 15 into the chamber 11, the vertical edge 19 and adjacent wall of the flame cup forming a distinct throat which directs the air more or less vertically into the chamber. The air then follows the path indicated by the arrows in FIG. 1 and, after fuel injection and ignition, the partly burnt mixture is directed out of the chamber 11 along the floor 18 and parallel groove 17 to the cylinder and valve pockets to complete the combustion process with the air remaining in the latter.

The embodiment produces desirable inflow characteristics by virtue of the provision of the vertical edge 19 which, together with the wall of the flame cup, and the two vertical side portions 19a (FIGS. 2, 4 and 6) of the flank portion 21 produces a well-defined vertical throat resulting in a chimney effect giving good inflow of air. The embodiment also produces desirable outflow characteristics by virtue of the inclination of the floor of the channel 20 which directs the partly burnt mixture to the outlet aperture 16, and by virtue of the flanks 21 which confine the main outflow of gaseous mixture to the central channel 20 which leads smoothly to the outlet aperture 16. Moreover, though of less importance, the raised flank portions 21 increase the compression ratio without interfering with the smooth shape of the combustion chamber 11.

FIG. 7 illustrates a modification of the FIGS. 2 to 6 embodiment in which the aperture 15 is of increased size to give alternative engine performance. The FIG. 7 flame cup is suitable for a high speed and high power output engine, but gives a high smoke level at low speeds. The FIG. 2 flame cup is suitable for a low speed, high torque engine and gives a reduced smoke level at such low speeds as will now be explained.

Engine characteristics derived from the present invention are illustrated in FIG. 8 which shows curves of power, torque and smoke number, on a base of engine speed. The smoke number referred to is a measure of the amount of smoke or unburnt carbon present in the exhaust gas of an internal combustion engine. When operating a diesel-engined vehicle it is desirable to operate so that the smoke emission of the engine is within acceptable limits.

The graphs of FIG. 8 show how the characteristics of a basic engine may be varied by selection of the flame cup. In the upper graph, curve X is illustrative of an acceptable smoke level above which the engine should not operate. The level will vary over a particular engine speed range in the manner shown. An engine designed for high power at high speeds such as a passenger car or marine engine will have a smoke level over the speed range corresponding to the full line curve A-A and will have corresponding power and torque curves as shown. It will be seen that at the lower end of the speed range the smoke rises rapidly above the acceptable smoke level and torque falls otf simultaneously. In the main speed range in which the engine is intended to operate, i.e., well above the maximum torque speed, the smoke level is well below the acceptable level up to and beyond the highest speed required. The engine would not normally be run at this speed for any length of time. The insert used for this type of engine would be the insert shown in FIG. 7 which has a large vertical aperture 15.

Where the same basic engine is required to give a good torque at low speeds, with a steep portion of the torque curve occurring as the engine speed falls from the rated full speed, the flame cup chosen is one with a relatively small vertical aperture 15 such as the one illustrated in FIG. 2. The maximum torque can be obtained lower down the speed range as shown on curve B-B, though the maximum power and speed are restricted. A limitation on power and speed is not a great disadvantage Where the engine is installed in a vehicle such as an agricultural tractor. In such a vehicle the large fluctuations in load imposed by the nature of the work require that the vehicle engine shall be capable of quickly meeting the load by a relatively small decrease in engine speed without exceeding the smoke limit.

With the embodiments of the invention it is possible to meet a wide range of engine specifications including a limitation asto smoke free performance, with a basic engine by the use of a range of flame cups, each of which costs a small fraction of the cost of the engine as a whole.

We claim:

1. In a compression ignition internal combustion engine having a cylinder and a cylinder head which includes a pre-combustion chamber, the combination comprising: a flame cup forming a portion of the chamber and including a continuous upstanding wall, a floor, an inlet aperture formed in the floor and including a vertical face, an outlet aperture formed in the wall and adjoining the inlet aperture, a channel formed in the floor and extending at an angle upwardly and away from the vertical face of the inlet aperture, the channel being aligned with the outlet aperture, and a channel formed in the cylinder head in alignment with and extending at the same angle downwardly and away from the outlet aperture, both channels and the outlet aperture together forming a smooth straight path for movement of a fuel mixture from the pre-combustion chamber to the cylinder.

2. A flalme cup according to claim 1 in which said inlet aperture is wider than said channel, and the flank portions which define said channel terminate at the inlet aperture in vertical faces flush with and one on either side of the aforementioned vertical face.

3. A flame cup according to claim 1 in which the floor of the flame cup, except at said outlet aperture, curves smoothly into the upstanding wall.

References Cited UNITED STATES PATENTS 3,238,931 3/1966 Rodrigues 12332 3,244,158 4/1966 Steidler 12332 LAURENCE M. GOODRIDGE, Primary Examiner U.S. Cl. X.R. l2332 

